Early diagnosis of Pneumocystis pneumonia and subsequent treatment reduces morbidity and mortality. Unfortunately current immunologic diagnostic procedures lack sensitivity and invasive procedures place the patient at risk. Use of better defined antigens may help overcome sensitivity problems. We propose a series of basic studies on antigenemia and antibody responses using the rat model system. This system enables us to control and manipulate host status with reference to disease chemotherapy history and recovery. In addition to our studies (in progress) on antigenemia and antibody responses in rats prior to, during induction and during recovery from pneumocystosis, we plan to examine the effect of non-specific pneumonitis and chemotherapy (TMP-SMZ) on these parameters. Also, emphasis will be placed on continued development of antibody reagents and purified antigens that can be used in our current ELISA antigenemia assays. Continued evaluation of our murine monoclonal antibody bank and creation of new rat infection- derived monoclonals will be done. The monoclonals will be evaluated in ELISA and Western immunoblot assays for potential value as detectors of circulating antigen. A necessary adjunct of these efforts will be the isolation and characterization of Pneumocystis antigens associated with various stages of infection and disease. Without pure antigens it will be more difficult to establish the relationship of antigenemia and antibody patterns to disease status. To this end combinations of gradient techniques, FPLC and affinity chromatography and preparative PAGE will be used to isolate proteins. These will be analyzed by Western blots and evaluated in ELISA against infection-derived sera taken at various stages of disease induction and recovery. We hope to better characterize Pc antigens and identify antigens relevant to the disease process. Finally we plan to investigate similarities between rat and human Pneumocystis. PAGE-Western immunoblot techniques will be used to characterize antigen banding patterns using rat and/or human infection sera or monoclonals as detectors. cDNA libraries will be established and homology analyses done to further clarify organism homology. This information may point to potential problems or opportunities in using these antigens in antigenemia or antibody assays of sera from humans. Most importantly, the cDNA library may enable use to obtain large quantities of pertinent Pc antigens.